Proposal #510

This is a proposal in response to an SG1 TFOP Special Call to observe Kepler 90 g, which has a transit duration of about 13 hours with a transit center of

Julian Day Number: 2460457.0036666663
UTC: 2024-05-26 12:05:17

Because of a high uncertainty it will be helpful to have at least a three-hour observation time through this time period:

UTC 2024-05-24 05:00 through 2024-05-28 19:00

---Text of SG1 TFOP Special Call---

Hi SG1 northern hemisphere observers,

We are sending this special call a bit early because I will be away from the office during the lead-up to this observing opportunity. Cristilyn Watkins will have the SG1 helm while I am away.

In short, we need observations with at least 1 ppt precision (in 10 minute bins) that cover 3 or more hours any time between:
UTC 2024-05-24 05:00 through 2024-05-28 19:00

The nominal ephemeris is under SG1 TOI 40.50 on the TTF. However, since the ephemeris uncertainty is +/-2 days, we have included a total of 33 TTF entries, staggered every 3 hours over the desired observing range (TOI-40.34 through TOI-40.66), which should produce a trigger to show an ingress or egress event for your observatory for any evening over the above observing range. Of course your TTF search setup should be set to look for partial transits rather than full transits (ingress/egress constraints set to "OR" instead of "AND"). Search for TIC 267667295 to show any of the staggered events.

Submit to SG1 and ExoFOP as usual (although there will be no real TOI on ExoFOP, so upload script users should set the TOI number to "-1").

Here are the details:

We have a special request from Lauren Weiss for observations of known planet Kepler-90 g, which has orbital period P = 210 days and significant TTVs. The next transit event is coming up on May 27th, although the large TTVs (25 hours, see figures below!) and the long time since the last transit was observed make it difficult to predict the exact transit time. The main goal with these observations is to prepare for a JWST proposal that would investigate this planet and its companion, Kepler-90 h, which are two large planets in an eight-planet system around a sun-like star. Anyone who contributes useful data (confirming or ruling out an ingress or egress over your observing window) will be invited to join the JWST proposal and would be invited as co-author on any resulting paper.

The target is in the Kepler field, so it is observable for at least half of the night from most northern hemisphere observatories.
RA
18h57m44.03s
DEC
+49d18m18.45s

The target star is faint at V = 13.9 and the depth is 3.8 ppt.

Use a red (r', R, i', I, z, Y, CBB) filter that gives the best photometric precision for your instrumentation.

The transit duration is 12.6 hours, so we are hoping to detect ingress and egress (approx. 1 hour in duration each) independently from different observatory locations.

The timing uncertainty is approximately +/- 2 days (95% confidence) due to TTVs and ephemeris degradation since the Kepler mission.

The nominal transit center in UTC is:
Julian Day Number: 2460457.0036666663
UTC: 2024-05-26 12:05:17

Three or more hours of observations over the time range below might be useful to detect or rule out an ingress or egress:
UTC 2024-05-24 05:00 through 2024-05-28 19:00